19,149 research outputs found
Balloon borne humidity and aerosol sensors
Infrared detectors for balloon sensing of aerosols and atmospheric moistur
Split-sideband spectroscopy in slowly modulated optomechanics
Optomechanical coupling between the motion of a mechanical oscillator and a
cavity represents a new arena for experimental investigation of quantum effects
on the mesoscopic and macroscopic scale.The motional sidebands of the output of
a cavity offer ultra-sensitive probes of the dynamics. We introduce a scheme
whereby these sidebands split asymmetrically and show how they may be used as
experimental diagnostics and signatures of quantum noise limited dynamics. We
show split-sidebands with controllable asymmetry occur by simultaneously
modulating the light-mechanical coupling and - slowly and out
of-phase. Such modulations are generic but already occur in optically trapped
set-ups where the equilibrium point of the oscillator is varied cyclically. We
analyse recently observed, but overlooked, experimental split-sideband
asymmetries; although not yet in the quantum regime, the data suggests that
split sideband structures are easily accessible to future experiments
Comparison of bungee-aided and free-bouncing accelerations on trampoline
Trampolines remain the single best apparatus for the training of aerial acrobatics skills. Trampoline use has led to catastrophic injuries from poor landings. Passive injury prevention countermeasures such as specialized matting have been largely ineffective. Active injury countermeasures such as hand spotting, âthrow-inâ mats, and overhead spotting rigs provide the most effective methods. The recent addition of several bungee cords between the ropes and the gymnastâs spotting harness has resulted in altered teaching and coaching of trampoline-related acrobatics. Bungee cords have eliminated the need for a coach/spotter to manage the ropes during skill learning. The purpose of this study was to assess the influence of the addition of bungee cords with a traditional rope-based overhead spotting rig. There is a paucity of any research involving trampoline injury countermeasures. Ten experienced trampoline acrobatic athletes (5 males, 5 females) from the U.S. Ski and Snowboard Association Aerials National Team performed 10 bounces as high as they could control. A triaxial accelerometer (200 Hz) characterized 10 bungee cord aided bounces and 10 freebounces on a trampoline from each athlete. Bed contact times, peak accelerations, and average accelerations were obtained. The results supported our hypotheses that the bungeeaided bounces achieved only 40% (average) to 70% (peak) of the free-bouncing accelerations (all Ï 0.092). The bed contact time was approximately 65% longer during the bungee-aided bounces (Ï < 0.001). Bungee cords may reduce the harshness of landings on trampoline
Implementation of a local principal curves algorithm for neutrino interaction reconstruction in a liquid argon volume
A local principal curve algorithm has been implemented in three dimensions
for automated track and shower reconstruction of neutrino interactions in a
liquid argon time projection chamber. We present details of the algorithm and
characterise its performance on simulated data sets.Comment: 14 pages, 17 figures; typing correction to Eq 5, the definition of
the local covariance matri
Optomechanical cooling of levitated spheres with doubly-resonant fields
Optomechanical cooling of levitated dielectric particles represents a
promising new approach in the quest to cool small mechanical resonators towards
their quantum ground state. We investigate two-mode cooling of levitated
nanospheres in a self-trapping regime. We identify a rich structure of split
sidebands (by a mechanism unrelated to usual strong-coupling effects) and
strong cooling even when one mode is blue detuned. We show the best regimes
occur when both optical fields cooperatively cool and trap the nanosphere,
where cooling rates are over an order of magnitude faster compared to
corresponding single-sideband cooling rates.Comment: 8 Pages, 7 figure
Glassy dynamics in granular compaction
Two models are presented to study the influence of slow dynamics on granular
compaction. It is found in both cases that high values of packing fraction are
achieved only by the slow relaxation of cooperative structures. Ongoing work to
study the full implications of these results is discussed.Comment: 12 pages, 9 figures; accepted in J. Phys: Condensed Matter,
proceedings of the Trieste workshop on 'Unifying concepts in glass physics
Validation of magnetophonon spectroscopy as a tool for analyzing hot-electron effects in devices
It is shown that very high precision hot-electron magnetophonon experiments made on n+nân+-GaAs sandwich device structures which are customized for magnetoresistance measurements can be very accurately modeled by a new Monte Carlo technique. The latter takes account of the Landau quantization and device architecture as well as material parameters. It is proposed that this combination of experiment and modeling yields a quantitative tool for the direct analysis of spatially localized very nonequilibrium electron distributions in small devices and low dimensional structures
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